If you are downloading many files using a download manager at once, you will most likely find that only a few files will download at a time. The rest will be queued. The direct download links will remain valid for 24 hours and are tied to your IP address (meaning they can't be shared with anyone else, as they will not work).

If you find that the links are expiring or showing up as invalid, the most likely cause of this is that you have reached the 24-hour limit, and need to request a new download link.

A direct download Premium download link looks like this:
http://s10.filefactory.com/get/p/9g43ikznntwz/a579c945421b2e39/thefilename.zip
[not a valid link - for display purposes only]

A normal file download URL looks like this:
http://www.filefactory.com/file/3g43ikznntwa/thefilename.zip
[not a valid link - for display purposes only]

When you click the download button on that page, these normal URLs never expire and are used to generate Premium download links.